If your period is regular and lasts 28 days, and if ovulation generally happens on day 14 of your cycle, then conception probably took place about two weeks after the LMP. For gestational age counting, these two weeks are added to a pregnancy as a simpler method than trying to track from ovulation or fertilization.

Do doctors add 2 weeks to a ultrasound?

Ultrasounds in Later Pregnancy Between 18 and 28 weeks of gestation, the margin of error increases to plus or minus two weeks. After 28 weeks, the ultrasound may be off by three weeks or more in predicting a due date.

Is two weeks pregnancy detectable?

Women can conduct an at-home pregnancy test by testing a sample of urine about two weeks after conception, or about the time a period is due. Home pregnancy tests have become more accurate in the last decade.